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Pre-MacMods
During Mendel’s genetic experiments, he noticed that pea pods could be either yellow or green. He figured out
that the allele for a green pod was dominant (G), while the allele for a yellow pod was recessive (g).
1. Complete a monohybrid cross for the following plant parents:
a. Plant with pea pod Gg
b. Plant with pea pod GG
Circle the answer that best completes the sentences:
2. The physical appearance of the pea pod is its genotype/phenotype.
3. The genetic makeup of the pea pod is its genotype/phenotype.
4. Is it possible for these parent plants to produce an offspring with yellow pea pods? Yes or no.
Lionfish Genetics
Introduction: Genetics is the study of patterns of inheritance and variations in organisms. Genes control each
trait of a living thing by controlling the formation of an organism’s proteins. Since in all cells (except gametes)
chromosomes are diploid (exist as a pair of chromosomes), each cell contains two genes for each trait, one on
the maternal chromosome and one on the paternal chromosome. The two genes may be of the same form or they
may be of different forms. These forms produce the different characteristics of each trait. The different forms
of a gene are called alleles. The two alleles are segregated during the process of gamete formation (meiosis II).
The law (principle) of dominance states that some alleles are dominant whereas others are recessive. An
organism with a dominant allele for a particular trait will always have that trait expressed (seen) in the
organism. An organism with a recessive allele for a particular trait will only have that trait expressed when the
dominant allele is not present.
The genotype (genetic makeup) of an organism reveals the type of alleles that an organism has inherited for
a particular trait. The genotype for a particular trait is usually represented by a letter, the capital letter
representing the dominant gene and the lower-case letter representing the recessive gene. The phenotype
(physical characteristics) of an organism is a description of the way that a trait is expressed in the organism.
Today we are going to explore lionfish genetics and practice using Punnett Squares to complete polygenic
crosses. You will be going on a scavenger hunt to find certain genotypes. First, we need to discuss the traits we
are interested in.
Lionfish coloration varies but can generally be described as light red or dark red. The alleles for the color trait
are R and r. The allele for light red is dominant and the allele for dark red is recessive.
1. What is the dominant allele?
2. What is the recessive allele?
Lionfish can have either long spines or short spines. The alleles for this trait are S and s. The allele for long
spines is dominant while the allele for short spines is recessive.
3. What is the dominant allele?
4. What is the recessive allele?
Lionfish can also have large mouths or small mouths. The alleles for mouth size are M and m. The allele for a
large mouth is dominant while the allele for a small mouth is recessive.
5. What is the dominant allele?
6. What is the recessive allele?
We are now going to figure out the possible genotypes for the given phenotypes.
Phenotype
Light Red
Dark Red
Long spines
Short spines
Large mouth
Small mouth
Genotype
You are now all going to become a lionfish with your own unique set of alleles. Half of you will be males and
half of you will be females.
7. Are you a male or a female lionfish?
8. What is your genotype?
9. What is your phenotype?
Now figure out all the possible combinations of alleles that you could pass on to your offspring. You should
have 8 different combinations. Write them on the lines below:
I have given you a blank strip of paper with eight boxes. Copy the allele combinations above into the boxes.
At the bottom of the page you will see 8 phenotypes of lionfish offspring. You will now go on a scavenger
hunt to find a mate that will allow you to produce each phenotype in the table below. When you find a mate,
you and your partner should use the paper you just filled out and the Punnett square to complete a polygenic
cross to make sure you are able to produce that particular offspring. You can only choose 2 offspring per
mate (so you need to find a minimum of 4 mates). Once you find your mate, write down number of your
fish and your mate’s fish in the box. If you are unable to produce a particular offspring put an X in the
“Mate’s fish Number” box. (HINT: you might want to fill out the genotype column before you begin).
Please watch the example before you begin.
Phenotype
Dark red, short spines,
large mouth
Light red, long spines,
small mouth
Dark red, long spines,
small mouth
Light red, short spines,
small mouth
Dark red, long spines,
large mouth
Light red, long spines,
large mouth
Light red, short spines,
large mouth
Dark red, short spines,
small mouth
Genotype
Your Fish Number
Mate’s Fish Number
Post-MacMods
A dog breeder wants to mate her Labrador retrievers and give the puppies to family members. Both dogs have
black fur and brown eyes. The allele for black fur (B) is dominant to the allele for yellow fur (b) and the allele
for brown eyes (E) is dominant to the allele for blue eyes (e).
1. Complete a dihybrid cross for the following dog parents:
a. Dog with alleles BBEe
b. Dog with alleles BbEe
Circle the answer that best completes the sentences:
2. The genetic makeup of the dog is its genotype/phenotype.
3. The physical appearance of the dog is its genotype/phenotype.
4. Is it possible for these parent dogs to produce an offspring with yellow fur and blue eyes? Yes or no.